Gohan is naturally kind and pure hearted, but the amount of things he's gone through made him cold, even if he does care. Tired of the pain he joins Goku Black after he saved him from near death, knowing he wasn't actually Goku but willing to live in the illusion. He doesn't agree with what they do and he doesn't participate in actively hurting anyone. Because of this he has become more reserved and cold than he was before. he stays far away from Trunks and is fine with him thinking he died.